Two of U.S. swimming’s biggest stars appear in form going into the world championships.

Katie Ledecky swam the world’s fastest 800m freestyle of 2019 at a Tyr Pro Series meet in Bloomington, Ind., on Sunday. A half-hour later in Atlanta, Caeleb Dressel clocked his fastest 100m freestyle since the summer of 2017.

It marked the last full meet for Ledecky before worlds in Gwangju, South Korea, in two months. Dressel will swim another meet in late June, his coach, Gregg Troy, said Monday.

Ledecky’s swim was a statement by virtue of the world rankings. She came to Bloomington as the world leader in the 800m, but only by four tenths of a second over Wang Jianjiahe, a 16-year-old who broke the Asian record at the Chinese Championships.

Nobody has been that close to Ledecky in her trademark event since her breakthrough 2012 Olympic title at age 15, though Ledecky and Wang have never been in the same race.

Ledecky opened breathing room in Bloomington, going four seconds faster than a month ago and winning by 26 seconds against a domestic field (Ledecky swept the 200m, 400m and 800m frees over the weekend and hasn’t lost domestically in any of those events in five years). She owns the 20 fastest 800m frees in history and on Sunday clocked the seventh-fastest of that set.

It’s an opportune time to look at the world rankings in the four individual events Ledecky will swim in Gwangju:

On paper, it’s the toughest competition Ledecky faces going into a major international meet since she expanded her program to include all of those events in 2014. Titmus, 18, is now the fifth-fastest 200m freestyler in history and the third-fastest in the 400m free. Wang is No. 3 all-time in the 800m and No. 6 in the 1500m.

The difficulty increases when putting history in perspective. Most elite female distance swimmers peak in their teens and, until recent years, were all but if not retired in their early 20s (Ledecky is 22).

Dressel’s performance last weekend triggered alarm bells to anybody who might have been sleeping on the man who earned a Michael Phelps-record-tying seven golds at the 2017 Worlds.

The summer of 2018 did not go to plan for Dressel, who earned two individual victories in seven tries between the two biggest meets of the year.

But in Atlanta, Dressel ran down Chase Kalisz in Saturday’s 200m butterfly, covering the last 50 meters 1.79 seconds faster than the field. Impressive for Dressel, a sprinter, to do that in an event he rarely contests and against Kalisz, the world’s greatest all-around swimmer whose primary event is the 400m individual medley.

Then on Sunday, Dressel moved from No. 27 to No. 4 in the world this year in the 100m freestyle. His 47.86 was his fastest 100m free since the 2017 Worlds, when Dressel recorded the three fastest 100m free times in American history.

The 2019 world rankings in Dressel’s primary events show that he, like Ledecky, could be in for a fight to repeat his 2017 medal haul:

Dressel’s winning times from 2017 Worlds in those three events were all significantly faster than Fratus, Grinev and Metella’s top times for 2019, but smart swimmers will be peaking in July and not at spring meets.

In other events Sunday, Annie Lazor continued her tear by clocking 2:20.77 in Bloomington’s 200m breaststroke and becoming the second-fastest American in history behind two-time Olympic champion Rebecca Soni.

Lazor, a 24-year-old who was seventh at the 2016 Olympic Trials, chopped 3.65 seconds off her personal best in the last 10 months. She leads the 2019 world rankings ahead of world champion Yuliya Yefimova of Russia. But Lazor did not qualify for the world championships team last summer.

Nathan Adrian ended his first meet since testicular cancer treatment (which included two surgeries) with a third-place finish in Sunday’s 50m freestyle. Adrian, a five-time Olympic champion, was fourth in the 100m free on Friday.

“I don’t really know what to make of the times, but in terms of my stroke, that felt better than I expected it to feel,” Adrian told Swimswam.com.

Rio Olympic gold medalist Lilly King posted the second-best time in the world this year in the 100m breaststroke at the Arena Pro Swim series in Atlanta on Sunday night. She raced to one minute, 6.20 seconds.

The fastest time in the world this year? Russia’s Yulia Efimova clocked 1:05.90 in April.

The two went head-to-head in a heated battle during the Games, the birth of the now-infamous “finger wag” incident. They’re expected to race again in as many as three breaststroke events at this summer’s world championships in Budapest in July. King told NBC Sports analyst Rowdy Gaines that she’s looking forward to breaking world records in the (non-Olympic) 50m and 100m breast in Budapest. She is also aiming to make the final in the 200m breast, something King was shut out of in Rio.

Chase Kalisz, the 400m individual medal silver medalist from Rio appeared to be in dominant shape in Atlanta. Kalisz raced a tough double Sunday night, explaining to Gaines that it was good practice for the 400m IM. First, he won the 200m butterfly in 1:55.94. He came back just under an hour later to win in the 200m IM in 1:57.21.

Katie Ledecky did not race Sunday night, but raced in the 800m freestyle in the morning heats. She cruised to 8:15.71, telling Gaines the time was about what she expected. Instead, she spent Sunday night on a flight back to school at Stanford.

Ledecky was close to her pool record of 4:00.31, set at the Atlanta meet one year ago. She came into the meet with the fastest time in the world this year of 4:01.01 from last month.

She looks to be in strong form coming off her freshman season at Stanford and going into the U.S. Championships in June, where the top two per event qualify for the world championships in July.

Ledecky also finished fifth in the 100m freestyle on Friday, 15 minutes before her 400m final. Stanford teammate and co-Olympic champion Simone Manuel won the 100m free in 53.82. Ledecky touched in 54.69.

The 100m free was billed as a showdown between Manuel and Canadian Penny Oleksiak, whom Manuel tied in Rio. But Oleksiak was a late scratch from the entire meet Friday due to family reasons, according to CBC.

The Atlanta meet continues Saturday and Sunday with finals from 7-8:30 p.m. ET, streamed on NBCSports.com/live and the NBC Sports app. NBCSN will also air live coverage Saturday.